How do i edit my username?

I am horrified that my username was changed while I was registering for this new MB. I cannot find any place to edit that back to what it was before it decided to spill my entire name as the logged in as. Can someone enlighten me?

I am determined to get used to this. I think I have set the font for Verdana and I left the cursor where it was before the font color choice I made, which is blue.